Edward Rosenthal, a lawyer representing the authors, said the project, "may benefit society in some instances," but it should be up to the copyright holder whether or not the work is displayed.

Further, the act of copying the books in and of itself violates the law, and copyright holders should at least be compensated, said Rosenthal, who called Google, "a copy shop for the 21st Century."

Chin countered by noting examples of people buying books after finding information about them through Google, suggesting the project can boost sales.

The authors have also argued that people could compile entire works for free by using various search terms.

Daralyn Durie, a lawyer for Google, said this is theoretically possible, but "extremely unlikely to happen," a sentiment Chin seemed to endorse.

"Is this a real concern?" Chin asked.

Chin also dismissed a suggestion from Rosenthal that the U.S. Congress should decide the issue.

"Does anything get done in Congress these days?" Chin said. "What are you suggesting? That I don't decide ... and wait for Congress?"

Chin's criticism of the plaintiffs' arguments echoed that of a three-judge panel of the 2nd U.S. Circuit Court of Appeals, which appeared to be skeptical of the lawsuit in July.

Google's project could have "enormous value for our culture," Circuit Judge Barrington Parker said in July. "This is something that has never happened in the history of mankind."

The 2nd Circuit ruled that Chin was premature in certifying the authors as a class without first deciding if the fair use defense under U.S. copyright law allowed Google to display snippets of books and returned the case to Chin.

Chin, who became an appeals court judge in the 2nd Circuit in 2010, but who retained jurisdiction over the case against Google at the district court level, did not rule on the question of fair use at Monday's hearing.

The case is Authors Guild Inc et al v. Google Inc, U.S. District Court, Southern District of New York, No. 06-cv-08136